We British are often considered endearingly eccentric by our foreign friends. But if the opinion polls are to be believed, I am very much afraid that they will shortly conclude that we are quite mad. How else to explain the apparent wish to put at risk the renaissance of Britain by electing those who strove to prevent its ever taking place?

Eighteen years of Conservative Government have transformed Britain into the most dynamic economy in Europe. "The past," wrote the novelist L. P. Hartley, "is a foreign country." And so great is the change wreaked in our country that those of us able to recall the dismal reality of the last Labour Government are inclined to rub our eyes and blink twice.

Even I sometimes find it hard to remember how truly dreadful conditions in socialist Britain were. Inflation then at over 25 per cent; now under three per cent. Top rate income tax then at 83 per cent – 40 per cent now. Nationalised industries then losing £50 million a week; privatised industries now contributing nearly £60 million a week to the Exchequer. Industrial relations transformed. Productivity transformed. Reputation transformed.

Politicians must, of course, expect to pay the price of their failures. And any government which holds office for such a long period makes some mistakes. Nobody except Mr Blair is perfect. But it is surely a new twist to political logic when politicians are expected to pay the price of their successes. Yet that is essentially why the Conservative Party now faces an uphill struggle for re-election.

Many people now feel so confident in Britain's future after our Conservative reforms that they think they can afford a change of government. More specifically, they feel that they can change the political faces, but preserve the political direction. The whole of Mr Blair's strategy in creating the boneless wonder that calls itself New Labour is to reassure the electorate in its illusion. But illusion it remains. The only real choice at the next general election is between Conservative policies and soft socialist policies. And the only way to be sure of getting Conservative policies is to vote Conservative. To coin a phrase, "There Is No Alternative".

I have on occasion been criticised because I won't conceal my welcome for the changes Mr Blair has made in his party's policies. It is surely good news that the Leader of the Opposition now rejects many of the policies his party has pursued – with his own enthusiastic endorsement – in the past. But this means neither that he has changed the reality of his party, nor that his own altered policies are best for Britain.

Since the Labour Party's fourth successive defeat at the 1992 general election, even the Labour Left has learnt the value of discretion. But sullen acquiescence should never be confused with genuine assent. It remains to be seen whether Labour MPs would allow a Labour administration, which had raised so many expectations and which would be unable to fulfil them, to stick to the austere self-disciplines set out by the shadow chancellor.

And how would a Labour Cabinet then react to mounting pressure to spend, borrow and inflate? The shadow chancellor's own proposed "windfall tax" on the privatised utilities to finance job creation schemes shows that New Labour has not really come to terms with its old error – namely, the illusion that it is government spending, rather than successful business, which generates real employment.

Similarly, Labour's plan to compel employers to recognise trade unions if supported by half of the "relevant workforce" reveals the depth of the party's remaining commitment to collectivism. It was precisely on this matter of union recognition that some of the worst cases of union militancy occurred — witness, most notoriously, the violent scenes at Grunwick 20 years ago. The truth is that the Labour Left doesn't believe in the party's apparently business-friendly policies — and the Labour leadership still doesn't understand the rationale behind them.

That's how it is with conversions of convenience. For what really matter in politics are convictions, principles and instincts. Of course, pragmatic calculations are also important. But it is what drives a man –or woman– that decides how he or she will react in the turbulent and perilous tasks of national leadership. That is why the alleged parallel between what Mr Blair has done for the Labour Party and what I and others of like mind did for the Conservative Party is false.

My approach – the approach which John Major has continued – was to return time after time to the basic truths about human nature, about markets, about limited government and about national pride, and build policies on these Tory foundations. The New Labour approach has been quite the opposite – to turn its back on its beliefs and adapt its policies to the requirements of pundits and pollsters. Imitation, someone said, is the sincerest form of flattery. But imitations are still fakes.

There is a further reason why the British people cannot afford the luxury of allowing novelty rather than rationality to determine their decision on May 1. This is because the next millennium looks like being much more than a notional watershed, because Western countries are facing a truly global economic revolution.

The success of British firms, the creation of British jobs and the level of British living standards increasingly depend on success in world markets, where even a mild flirtation with anti-enterprise policies can lead to sudden disaster. In such a world only the countries which, like America and Japan, keep public spending low, taxes down and regulation light can compete successfully. Britain has to be among them.

The big-spending, over-borrowing, high-taxing and heavy-regulating governments of continental Europe know that they cannot deliver economic success to their people. So they turn, as socialists of all descriptions ultimately turn, to intervention in industry, to trade protection and – now – to European federalism. It is, therefore, no surprise to me that the Labour Party which favours the economic and social model that dominates continental Europe is also anxious to give away more and more powers to Brussels over our affairs. Nor does it surprise me that this same European model is in practice rejected by rioting Belgians, striking Frenchmen, picketing Germans and jobless Spaniards. The claim that socialism existed to benefit workers rather than bureaucrats and self-serving intellectuals was always false: and it is no less false today.

But in one crucial area Labour does pose a quite new and sinister threat. In the last resort, it is the constitution of a state that stands between the established liberal legal order and those who seek to destroy it: and here the Labour Party's hesitant retreat from socialist economics has been more than matched by its race towards radically subversive proposals for constitutional change. Labour wishes to turn the House of Lords into a glorified quango, swamped with appointed socialist peers; they are prepared to risk shattering the United Kingdom by erecting a Scottish Parliament that would demand ever-greater powers; they are toying with proportional representation, which could banish strong, principled government for ever; they have nodded and winked their way into the affections of Euro-federalists in Bonn and Brussels by their willingness to barter away parliamentary sovereignty and national independence. If these things come to pass Britain will indeed, and in a different way, become "a foreign country". But what the British people have to ask themselves before May 1 is whether they would want to live in it.